Clinical effectiveness of direct resin composite restorations bonded using one-step or two-step self-etch adhesive systems: A three-year multicenter study.

The purpose of this multicenter clinical study was to compare the mid-term clinical effectiveness of direct resin composite restorations using one-step or two-step self-etch adhesives (1-SEAs or 2-SEAs). In total, 352 restorations of class I-V cavities and non-carious cervical lesions in vital teeth (1-SEAs; 52 cases, 2-SEAs; 300 cases) were placed at nine university hospitals and evaluated according to the modified USPHS criteria at baseline, and after 1, 2, and 3 years. The recall rates were 86.6% (1 year), 80.1% (2 years), and 62.2% (3 years). Two restorations failed due to fracture during the follow-up, and there was no significant difference in survival rates between 1-SEAs (97.6%) and 2-SEAs (99.4%). However, 2-SEAs exhibited significantly lower occurrences of discoloration, marginal discoloration, fracture, and plaque retention. Moreover, the subjects reported a significantly lower postoperative hypersensitivity and higher overall satisfaction at all evaluation periods if 2-SEAs were used.

Effect of acid erosion on enamel bond strength of self-etch adhesives and sonic velocity measurement of enamel.

The purpose of this study was to investigate the effect of acid erosion on the bonding performance of universal adhesives. Freshly extracted bovine teeth were cut into enamel slabs and assigned to either the Er or the control group. Specimens in the Er group were immersed in citric acid solution (pH 2.1) twice a day and stored in artificial saliva, while control specimens were simply stored in artificial saliva. Differences in the mean values between the control and Er groups were greater than expected, despite accounting for the effect of differences in the adhesive systems (p=0.016). The Er group mainly exhibited cohesive failure in the enamel, while adhesive failure was more frequent in the control group. The sonic velocity was found to decrease over time in the acid attacked specimens. The results indicated that bond strengths of universal adhesive tested increased in eroded enamel.

Three-year clinical evaluation of posterior composite restorations placed with a single-step self-etch adhesive.

In this clinical study, we evaluated the 3-year clinical performance of a resin composite containing a surface-prereacted glass ionomer (S-PRG) filler (Beautifil II; Shofu Inc., Kyoto, Japan) placed with a single-step self-etch adhesive (BeautiBond; Shofu Inc.) in posterior restorations. Using modified US Public Health Service criteria, two experienced investigators performed clinical evaluations at the baseline, 6 months, 18 months, and 3 years. Color match, marginal adaptation, anatomical form, surface roughness, marginal discoloration, postoperative sensitivity, and secondary caries were evaluated. After 3 years, 26 patients attended the recall and 31 restorations were evaluated. No postoperative sensitivity or secondary caries was observed at any time point, and no restorations failed during the follow-up period. However, surface roughness, marginal adaptation, and marginal discoloration showed deterioration after 3 years. In conclusion, although some clinical changes were observed, resin composite containing S-PRG filler placed with self-etch adhesive exhibited acceptable clinical behavior in posterior restorations.

Influence of methyl mercaptan on the repair bond strength of composites fabricated using self-etch adhesives.

The influence of methyl mercaptan on the repair bond strength of composites fabricated using self-etch adhesives was investigated. The surface free-energies were determined by measuring the contact angles of test liquids placed on composites that had been immersed in different concentrations of methyl mercaptan (0.01, 0.1, and 1.0 M). To determine the repair bond strength, self-etch adhesives were applied to the aged composite, and then newly added composites were condensed. Ten samples of each specimen were subjected to shear testing at a crosshead speed of 1.0 mm min(-1). Samples were analyzed using two-way ANOVA followed by Tukey's honestly significant difference (HSD) test. Although the dispersion force of the composites remained relatively constant, their polar force increased slightly as the concentration of methyl mercaptan increased. The hydrogen-bonding forces were significantly higher after immersion in 1.0 M methyl mercaptan, leading to higher surface-free energies. However, the repair bond strengths for the repair restorations prepared from composites immersed in 1.0 M methyl mercaptan were significantly lower than for those immersed in 0.01 and 0.10 M methyl mercaptan. Considering the results of this study, it can be concluded that the repair bond strengths of both the aged and newly added composites were affected by immersion in methyl mercaptan solutions.

Influence of environmental conditions on orthodontic bracket bonding of self-etching systems.

The influence of temperature and relative humidity (RH) on the bond strength of orthodontic adhesives was investigated. Two self-etching/composite type, one acid-etching/composite type, and one acid-etching/PMMA type of adhesives were examined under different temperature and RH conditions. Orthodontic brackets were bonded to bovine enamel, and shear bond strength test was performed at a crosshead speed of 1.0 mm/min after 24-hour storage in 37 degrees C water. Data were analyzed by Tukey's HSD test. Each specimen was assigned an ARI score. All the materials tested exhibited their highest bond strength under room conditions at a range of 10.4-17.0 MPa. Conversely, when under a lower RH condition, bond strength for all the systems ranked the lowest within a range of 6.8-12.0 MPa, with bond failure at the bracket-adhesive interface. These results demonstrated that care should be exercised when using orthodontic adhesive systems in the oral environment.

Effect of prior acid etching on bonding durability of single-step adhesives.

This study investigated the effect of prior phosphoric acid etching on the enamel bond strength of five single-step self-etch adhesive systems: Absolute, Clearfil tri-S Bond, Fluoro Bond Shake One, G-Bond and One-Up Bond F Plus. Bovine mandibular incisors were mounted in self-curing resin, and the facial surfaces were wet ground with #600 silicon carbide paper. Adhesives were applied to the enamel surfaces with or without prior phosphoric-acid etching and light irradiated. The resin composites were condensed into a mold and light irradiated. In total, 40 specimens were tested per adhesive system with and without prior acid etching and were further divided into two groups: those stored in water at 37 degrees C for 24 hours without cycling and those stored in water at 37 degrees C for 24 hours followed by thermal cycling between 5 degrees C and 55 degrees C with 10,000 repeats. After storage under each set of conditions, the specimens were tested in shear mode at a crosshead speed of 1.0 mm/minute. Two-way analysis of variance, the Student's t-test and the Tukey HSD test were used to analyze the data at a significance level of 0.05. For the specimens without prior acid etching, the mean bond strengths to enamel ranged from 11.0 to 14.6 MPa after 24-hour storage in water, while the corresponding values for specimens with prior acid etching ranged from 15.2 to 19.3 MPa. When these specimens were subjected to thermal cycling, the mean bond strengths ranged from 11.3 to 17.0 MPa without prior acid etching and from 12.3 to 23.2 MPa with prior acid etching. The changes in enamel bond strengths differed among the adhesive systems tested. After 24-hour storage in water, the most common failure modes were adhesive failure and mixed failure for specimens with and without prior acid etching, respectively. Thus, through a careful choice of adhesive system, prior acid etching can increase the bond strengths of single-step self-etch adhesive systems.

One-year clinical evaluation of five single-step self-etch adhesive systems in non-carious cervical lesions.

This study evaluated the clinical performance of five single-step self-etch adhesive systems over a one-year follow-up period in 98 restorations. Independent evaluations were performed at baseline (one week), after three months, six months, and one year, by two trained examiners using the modified US Public Health Service rating criteria. Color match, marginal integrity, anatomical form, surface roughness, marginal or interfacial staining, postoperative sensitivity, and secondary caries were evaluated. Results were analyzed using the Kruskal-Wallis test at a significance level of p<0.05. After one year, the restorations were re-evaluated and 100% retention rate was recorded. No caries were detected in association with any of the restorations. Marginal adaptation was the only measure that showed a slight deterioration over time, and there were no significant differences in this factor among the adhesive systems tested (p=0.464).

Determination of elastic modulus of demineralized resin-infiltrated dentin by self-etch adhesives.

The purpose of this study was to determine ultrasonically the changes in elastic modulus of demineralized adhesive-infiltrated dentin. Dentin disks were obtained from bovine incisors and shaped into a rectangular form. The specimens were immersed in single-step self-etch adhesives, then stored in distilled water and run through thermal cycles between 5 and 60 degrees C. The longitudinal and shear wave sound velocities and the elastic modulus were determined using ultrasonic equipment composed of a pulser-receiver, transducers, and an oscilloscope. After 24 h of storage, the elastic modulus of mineralized dentin was 16.9 GPa and that of demineralized dentin was 2.1 GPa. The immersion of demineralized dentin in adhesives significantly increased the elastic modulus to 3.3-5.9 GPa. After 30,000 thermal cycles, the elastic modulus of dentin was 32.4 GPa, whereas that of demineralized adhesive infiltrated dentin was 3.1-4.1 GPa. Thermal stresses did not cause adhesive-infiltrated demineralized dentin to deteriorate, as measured by elastic modulus.

Influence of thermal cycling on dentin bond strengths of single-step self-etch adhesive systems.

This study investigated the influence of thermal cycling on the dentin bond strengths of single-step self-etch adhesive systems. The Absolute, Clearfil Tri-S Bond, G-Bond and One-Up Bond F Plus systems were used. Bovine mandibular incisors were mounted in self-curing resin, and the facial surfaces were wet ground with #600 SiC paper. Adhesives were applied to the prepared dentin surfaces, and they were light irradiated according to each manufacturer's instructions. Resin composites were condensed into a mold (4 mm in diameter and 2 mm in height) and light irradiated for 30 seconds. Bonded specimens were divided into three groups and subjected to different storage conditions as follows: 37 degrees C water for 24 hours; 37 degrees C water for 24 hours followed by 10,000 thermal cycles between 5 degrees C and 60 degrees C or 37 degrees C water for 24 hours followed by 20,000 thermal cycles between 5 degrees C and 60 degrees C. Ten samples per group were tested in a shear mode at a crosshead speed of 1.0 mm/minute. Analysis of variance and Tukey's HSD test at the 0.05 significance level were used to compare the three storage conditions for each adhesive system. After 24 hours storage in water, the mean dentin bond strengths ranged from 11.4 MPa to 17.1 MPa. The Clearfil Tri-S Bond system showed the highest bond strength. After 10,000 thermal cycles, the mean bond strengths remained unchanged except for those of the Clearfil Tri-S Bond system, which significantly increased. Significant decreases in bond strength were observed for the Absolute and One-Up Bond F Plus systems after 20,000 thermal cycles. Failure mode was commonly due to adhesive breakdown associated with partial cohesive failure of the adhesive resin. From the results of this study, in terms of simplifying the clinical procedure, the benefit of using single-step self-etch systems might be acceptable.

Comparison of two methods for measuring the polymerization characteristics of flowable resin composites.

OBJECTIVES: The purpose of this study was to compare two methods for assessing the polymerization characteristics of flowable resin composites. METHODS: Two different flowable resin composites and a hybrid resin composite control were investigated. In order to measure the volumetric shrinkage (DeltaV), each material was placed into a mould and extruded into a water-filled dilatometer. The specimens were then light irradiated for 30s using a curing unit with the power density adjusted to either 100 or 600mW/cm(2). For the speckle contrast measurement, each resin composite was condensed into a glass tube and irradiated. The laser-speckle field was recorded in a digital frame. The calculated values were obtained for each pair of adjacent patterns and the changes in speckle contrast as a function of time were obtained. RESULTS: The average DeltaV values of the resins after 180s ranged from approximately 3.3 to 4.4% for the flowable composites and from approximately 1.8 to 2.3% for the hybrid composite control. The overall magnitude of the speckle contrasts decreased soon after the initial light exposure commenced and gradually increased thereafter. The speckle contrast measurements revealed changes in the pastes due to the polymerization of the flowable resins that were greater than those obtained with the water-filled dilatometer. SIGNIFICANCE: These data suggest that the polymerization characteristics of flowable resins can be measured successfully using two different methods. Moreover, our findings are of clinical relevance, as the data obtained under laboratory conditions might give an indication of the suitability of flowable resin composites for specific clinical applications.

Influence of moisture conditions on dentin bond strength of single-step self-etch adhesive systems.

This study was conducted to clarify the influence of dentin surface moisture on bond strength of single-step self-etch adhesive systems. The adhesive systems used were Adper Prompt L-Pop (AP), Clearfil tri-S Bond (CT), Fluoro Bond Shake One (FB), G-Bond (GB), and One-Up Bond F Plus (OF). Bovine mandibular incisors were wet-ground with #600 SiC to expose the labial dentin. After rinsing with tap water, the dentin surface was dried with air for 10 sec (Dry condition) or blotted (Wet condition). Adhesives were applied according to each manufacturer's instructions, followed by resin composite polymerization. Ten samples per test group were stored in distilled water at 37 degrees C for 24 h, then shear tested at a crosshead speed of 1.0 mm/min. The data were analyzed by Student's t test and Tukey HSD test at a probability level of 0.05. The mean bond strengths for Dry condition ranged from 13.9 MPa to 18.2 MPa, and those for Wet condition ranged from 7.1 MPa to 18.4 MPa. Significantly lower bond strengths were obtained for the Wet condition for GB, FB, and OF. Failure after the test was commonly due to adhesive breakdown associated with partial cohesive failure in the dentin. These data suggest that air-drying of the dentin surface is appropriate for the adhesive systems tested.

Effect of thermal cycling on enamel bond strength of single-step self-etch systems.

This study investigated the influence of thermal cycling on the enamel bond strength of single-step self-etch adhesive systems. The systems used were Absolute, Clearfil tri-S Bond, G-Bond and One-Up Bond F Plus. Bovine mandibular incisors were mounted in self-curing resin, and the facial surfaces were wet ground with #600 SiC paper. Adhesives were applied on the prepared enamel surfaces and light irradiated according to each manufacturer's instructions. Resin composites were condensed into a mold (ø4x2 mm) and light irradiated for 30 seconds. Thirty specimens per adhesive systems were divided into 1 of 3 test groups (n=10) following storage in water at 37 degrees C for 24 hours. The specimens were then stored in 37 degrees C water for 24 hours, followed by thermal cycling 10,000 and 20,000 times between 5 degrees C and 60 degrees C. After each storage condition, the specimens were tested in shear mode at a crosshead speed of 1.0-mm/minute. One-way ANOVAs and Tukey HSD test at a level of 0.05 were conducted. After 24 hours of water storage, the mean enamel bond strengths ranged from 11.3 to 16.9 MPa, and Clearfil tri-S Bond showed significantly higher bond strength. After thermal cycling, the mean bond strengths ranged from 8.3 to 20.7 MPa. The changes in enamel bond strengths were different among the adhesive systems tested. Failure modes after the test were commonly adhesive failure associated with partial cohesive failure adhesive in resin. With a careful choice of adhesive systems, the benefit to using single-step self-etch systems in terms of simplifying the clinical procedure might be acceptable, even after thermal stresses.

Effect of thermal cycling on bond strengths of single-step self-etch adhesives to bovine dentin.

The purpose of this study was to clarify the effect of thermal cycling on dentin bond strengths of single-step self-etch adhesives. Five commercially available single-step self-etch systems were used. The adhesives were applied to the dentin surfaces of bovine incisors, and then light-irradiated. Resin composites were condensed into a mold and light-irradiated. Bonded specimens were divided into two groups and stored in water at 37 degrees C for 24 h without thermal cycling, or in water at 37 degrees C for 24 h followed by 10,000 thermal cycles between 5 degrees C and 60 degrees C. Ten samples per group were tested for shear strength at a crosshead speed of 1.0 mm/min. The data were analyzed by Student's t test and Tukey HSD test at a probability level of 0.05. After 24 h of storage in water, the mean dentin bond strengths ranged from 9.3 MPa to 14.0 MPa. After 10,000 thermal cycles, the mean bond strengths remained unchanged. Failure after the test was commonly due to adhesive breakdown associated with partial cohesive failure of the resin. The present results suggest that the benefit of using single-step self-etch systems, in terms of simplifying the clinical procedure, might be acceptable even after thermal stresses.

Influence of light intensity on dentin bond strength of self-etch systems.

The purpose of this study was to investigate the influence of light intensity on dentin bond strengths of four self-etch adhesive systems. The light intensities used to polymerize specimens were controlled at levels of 150, 300, 600, and 900 mW/cm2. The two-step self-etch adhesive systems Imperva Fluoro Bond and Mac Bond II, and the one-step self-etch systems Fluoro Bond Shake-One and One-Up Bond F Plus were used with their corresponding light-cured resins. Labial surfaces of lower bovine incisors were ground with #600 grit SiC paper to expose the dentin. The dentin surfaces were treated according to each manufacturer's instructions and bonded with resin composites. A shear bond strength test was performed and the data were analyzed by one-way ANOVA followed by Newman-Keuls multiple comparison at a level of 0.05. Statistical analysis of the data indicated that light intensity affected the dentin bond strengths of the adhesive systems tested. Significantly lower bond strengths were obtained by exposure to 150 mW/cm2, and there were no differences between the bond strengths obtained at 600 and 900 mW/cm2 for all the adhesive systems used. Further research will be required to clarify the irradiance-dependent properties of light-cured resin adhesive systems.

Influence of crosshead speed on micro-tensile bond strength of two-step adhesive systems.

OBJECTIVES: The purpose of this study was to determine the influence of crosshead speed on the micro-tensile bond strength of two separate adhesive systems to dentin. METHODS: The systems used were the Clearfil SE Bond (Kuraray Medical) and the Single Bond (3M ESPE) combined with a resin composite Clearfil AP-X (Kuraray Medical). Dentin surfaces of bovine madibular incisors were primed with self-etching primer followed by air blowing for Clearfil SE Bond, or etched with phosphoric acid followed by rinsing with distilled water for Single Bond, and adhesive was applied. The resin composite was then built up in three layers and light activated. After 24 h storage in water, specimens were sectioned and trimmed to a cross-sectional area of 1 mm(2) and subjected to a micro-tensile bond-strength test. Ten samples per test group were tested at crosshead speeds of 0.5, 1.0, 5.0 and 10.0 mm/min. Micro-tensile bond-strength values (in MPa) were calculated from the peak load at failure divided by the specimen surface area. Two-way ANOVA was performed at the 0.05 probability level. RESULTS: The mean dentin bond strength at different crosshead speeds ranged from 34.6 to 37.1MPa for Clearfil SE Bond and from 44.3 to 50.4 MPa for Single Bond. There was no significant difference among the same adhesive systems with the different crosshead speeds tested. SIGNIFICANCE: The influence of the crosshead speed might be negligible when measuring micro-tensile bond strengths.

Influence of light activation on the volumetric change of core foundation resins.

A core foundation system is frequently used in endodontically treated teeth that suffer excessive loss of the coronal portion of their structure. The volumetric shrinkage of core foundation resins may create marginal gaps that influence the bonding ability and longevity of a restored tooth. Little is known about how activation conditions of resin core foundation resin pastes affect their volumetric shrinkage. This study evaluated the influence of light intensity and light activation duration on volumetric shrinkage of direct core foundation resins. Two dual- and one light-activated core foundation resin pastes were employed. The material was placed in a Teflon mold 4 mm in diameter and 2 mm in height and extruded into a water filled dilatometer. The specimens were then light activated and the change in height of the meniscus of water was recorded using a charged-coupled device camera. The average volumetric shrinkage of the core foundation resins after 180 seconds ranged from 1.53% to 2.63%. For all materials tested, there was a tendency for increased volumetric shrinkage with increased light activation time and intensity. The results of this study indicate that the volumetric change of core foundation resins is influenced by the time and intensity of light activation.

Influence of polishing duration on surface roughness of resin composites.

There is a need for effective polishing instruments for resin composite restorations with highly polished surfaces. The purpose of this study was to investigate the influence of polishing duration on surface roughness of light-cured resin composites. Four polishing systems, Compomaster (Shofu), Silicone Points C Type (Shofu), Super Snap (Shofu) and Enhance Finishing and Polishing System (Dentsply/Caulk), were used to polish two commercially available resin composites, Clearfil AP-X (Kuraray Medical) and Lite-Fil II A (Shofu). Resin pastes were condensed into molds (10 mm in diameter, 5 mm in depth) and light irradiated for 40 s. Composite surfaces were ground with # 600 SiC paper followed by polishing with an instrument for 30 s, and the surface roughness was measured every 10 s during polishing procedures. The average surface roughnesses (Ra) were determined using a profilometer. Data were analyzed by Tukey HSD test (P = 0.05). After 30 s of polishing, mean Ra values ranged from 0.07 to 0.50 for Clearfil AP-X, and from 0.11 to 0.57 for Lite-Fil II A. Although the time required for polishing was longer, the surface finish produced by multiple-step polishing systems was superior to that obtained with one-step polishing systems.

Effect of metal conditioners on polymerization behavior of bonding agents.

This study aimed to determine the influence of metal conditioners on the polymerization behavior of bonding agents. Bonding agents of two-step self-etching primer systems and metal conditioners for adhesion of dental metal alloys were used. Double bond conversion was determined by Fourier transform-ation infrared spectroscopy. The percentage of residual double bonds, including pendant and monomeric double bonds, was calculated by comparing the obtained ratio with that of the uncured bonding agent. The degree of conversion of the bonding agents was obtained by subtracting the remaining double bonds from 100%. ANOVA followed by a Tukey HDS test was performed. Degree of conversion of the bonding agents ranged from 86.0 to 87.8%. When the bonding agents were mixed with metal conditioners or solvents of the metal conditioners, double bond conversion of the bonding agents tended to decrease. Within the limitations of this study, which was far removed from clinical situations, the presence of metal conditioners and remaining solvents had adverse effects on the polymerization reaction of bonding agents. Clinicians should be cognizant of the various factors that can influence bond strength of restorative resins to dentin.

Effect of metal conditioner application on bond strength of luting cements to a noble metal.

The purpose of this study was to evaluate the adhesive performance of luting cements to a noble metal alloy treated with metal conditioners. Cast disk specimens made of a noble metal alloy were gritblasted with alumina followed by no treatment or priming with two different types of metal conditioner. A mold was placed on the metal surface and filled with luting cement. Ten samples per test group were stored in 37 degrees C distilled water for 24 hours, then shear tested at a cross-head speed of 1.0 mm/minute. ANOVA and Tukey's HSD tests (alpha=0.05) were done. The mean bond strength of resin-modified glass ionomer cement increased significantly with metal conditioner application compared to the controls, indicating the efficacy of the tested metal conditioners in improving bond strength. Based on the results of this study, it seemed to be a useful method to incorporate a functional monomer into resin cements so as to improve the bond strength to a noble metal alloy.

Real-time dimensional change in light-cured composites at various depths using laser speckle contrast analysis.

Laser speckle contrast analysis is an interferometric technique that is used to measure the displacement of the rough surface of a specimen. The purpose of this study was to present a laser speckle correlation method for monitoring real-time dimensional changes of light-cured composites. Uncured composite was condensed into a glass tube and irradiated for 30 s with 600 or 200 mW cm(-2). The speckle patterns obtained from lateral and bottom composite surfaces were monitored using a speckle analyser. The speckle field is recorded in a digital frame and stored by image processing system as the carrier of information on the displacement of the tested surface. The calculated values were obtained for each pair of adjacent patterns and the changes in speckle contrast as a function time were obtained from five repeated measurements. The overall magnitude of the speckle contrasts decreased soon after the initial light exposure and gradually increased thereafter. The speckle contrasts obtained from the bottom surface were smaller than those obtained from the lateral surface. This tendency was more pronounced when the specimen was irradiated with lower power density. It can be concluded that monitoring differential shrinkage at various levels of depth can be achieved with this new technique.